I tried it without the back strap at first and then tried with the thickest one. My hand isn't big enough to get a good grip with the back strap so, I went back to no back strap and my groups actually improved.
I purchased both of my gen4's because of how they feel with out any of the back straps. I also think they look like crap with any of the straps on. They mess up the lines of the gun. Glock should have taken some lessons from Springfield on the straps.
Webphiser, you dont have to have that tool. Any small solid object will work, ive pushed all 3 pins out before with an ink pen in a pinch.
I love the backstraps.. I use the largest one. I had a hell of a time getting the houge on after that but I like the feel of it. I do have giant meatmittens though...the extra strap plus houge was way to much for my friend. So to each his own... I think they work good. I also got a beavertail that is fun to use at times. I put the medium strap + beavertail and houge on. A pain but fun at the range..
Ya I used the tool built into my dads M&P 9 to put on the back strap. Once I got it on the first time it was easier. Today I finally get to go put it through its paces, more than the 10rnds I did when I bought it, so I'll get to test which one I want, if any.